Which will experience the greater effective nuclear charge?

Question

The electrons in the n=3 shell in Ar or the n=3 shell in Kr? And which will be closer to the nucleus?

Answer 1

For Ar, you have 1s2 2s2 2p6 3s2 3p6 with 8 valence electrons (n=3) and 10 non valence electrons (shielding)

Zeff = 18- 10 = +8

 

The n=3 shell electrons in Kr are the same as for Ar but Kr has 36 protons whereas Ar has only 18 protons.  So, the Zeff would be greater for n=3 electrons in Krypton.  36 - 10 = 16 compared to 8 as Zeff